The present invention relates to a method and apparatus for depositing metal into high aspect openings using a cathodic vacuum arc as a source of metal ions. Typically, the metal is deposited to create field emission display tips or deep contacts on a substrate. When used in the production of field emission tips, the tips are fabricated using the Spindt technique with the tip deposition step performed via the cathodic arc.
Coatings produced by traditional physical vapor deposition (PVD) techniques, such as electron-beam evaporation and magnetron sputtering, are adequate for some purposes. However, as explained in U.S. Pat. No. 5,279,723 to Falabella et al., the disclosure of which is incorporated herein by reference, there are increasing instances where coatings produced by a PVD technique have inadequate stoichiometry, adhesion, or density and are too isotropic. In the case of high aspect openings, sputtering can result in the opening being pinched off rather than becoming coated throughout its entire depth.
Ion-based coating methods provide the ability to control the directionality of the ions. Ion sources involving vacuum arc-based processes may overcome the difficulties of the PVD techniques by providing copious quantities of ions of virtually any conductive material. The ion beam can be highly directional thus eliminating the need for the filters used in sputtering systems. Vacuum arc coating techniques generally involve use of either an anodic arc or a cathodic arc. Unfortunately, cathodic arcs normally produce droplets of material called "macro-particles" which cause blemishes in the resulting coatings. An example of one system directed toward removing these macro-particles can be found in U.S. Pat. No. 5,279,723.
Field emitter arrays have been formed using the "Spindt" technique in which a metal, such as molybdenum, is evaporated into a masked hole in a electric. The evaporated metal is first filtered in order to form a very directional (or anisotropic) beam of material.
The known filtering techniques have had limited application in mass production because of cost and efficiency. They have been generally difficult to perform over large areas and the filter has required frequent cleaning and/or changing in order to remove build up.